Circuit interrupter



May 28 1946.

L. R. LUDWIG ET AL 8,

CIRCUIT INTERRUPTER I;

Filed March 9, 1940 3 Sheets-Sheet 2 INVENIORS Leon 1?! Ludwg andSen/gnu)? a/(er f? ATTORN y 6- 1.. R. LUDWIG ET AL 2,401,008

CIRCUIT INTERRUPTER Filed March 9, 1940 3 Sheets-Sheet 3 INVENT ORSLean/P. Ludw/y and fienjgmgfifiaken q ATTQRNE? WITNESSES: 6 1 7% WM 5Patented May 28, 1946 CIRCUIT INTERRUPTER Leon R. Ludwig, Forest Hills,and Benjamin P. Baker, Turtle Creek, Pa., assignors to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation ofPennsylvania Application March 9, 1940, Serial No. 323,214

26 Claims.

This invention relates to improvements in circuit interrupters, and moreparticularly to operating mechanisms for interrupters of the fluidoperated type.

In the patent of A. H. Bakken, No. 2,282,154, issued May 5, 1942, andassigned to the assignee of this application, is shown and described acircuit interrupter of the gas-blast type utilizing compresed gas, suchas air, to extinguish the arc and also to actuate appropriate mechanismfor operating the contact structure to open and closed circuitpositions. The instant invention is di rected more specifically to themechanical operation of a circuit interrupt r of the aforesaid type,although the particular operating mechanism disclosed is not necessarilylimited in its use in connection with an interrupter of the airblasttype, and may with equal advantage be used in connection with airbreakers other than that disclosed and also breakers of theliquid-immersed type.

The main object of our invention is to provide an improved operatingmechanism of the fluid pressure actuated type that is simple and ruggedin construction and capable of efiicient and reliable operation.

A further object of our invention is to provide a fluid pressureactuated operating mechanism for circuit interrupter-s that is capableof effecting high-speed opening and closing of the interrupter contactswithout subjecting the contact structure and associated mechanism tosevere shocks and strains.

It is also an object of our invention to provide a gas pressure actuatedoperating mechanism for circuit interrupters that possesses a highdegree of flexibility in operation, so as to render the interruptertrip-free on overload, and in any other respect make it equivalent totrip-free mechanical mechanisms, but without the use of mechanicallatches or mechanical trip-free devices.

Other objects and advantages relate to the various parts of theoperating mechanism, as the operating piston, control valves, gaspressure supply and the arrangement thereof, and will appear more fullyin the following description when read in connection with theaccompanying drawings, in which:

Figure 1 is a front elevation View of a gas-blast circuit interrupterembodying the principles of our invention;

Fig. 2 is aside elevation View, partially in section, showing thecircuit interrupter illustrated in Fig. 1;

Fig. 3 is a cross-sectional view taken through one of the auxiliary gasstorage tanks at III-III of Fig. 2;

Fig. 4 is a further sectional view of a portion of one of the auxiliarygas storage tanks taken along the line IV-IV of Fig. 3; and

Fig. 5 is an elevation view, partially in section, of the operatingcylinder of the operating mechanism and the control valves therefor.

Referring to the drawings, the reference numeral 6 designates the maintank for storing gas, such as air, under pressure. Extending from thetop of the tank 6 are three flanged conduits 8 which, in turn, carry ametallic valve casing it. Mounted upon the upper end of each valvecasing I9 is a tubular insulator I2 which, in turn, has secured to itsupper end an arc chute support M also of insulating material. Thesupport It has mounted thereon a stationary contact 16 provided with anexternal circuit terminal I8. A throat-like gas passage 20 extendsthrough the support [4, and is preferably coextensive with the passagethrough the tubular insulator l2. This throat-like passage 20 opens intoan arc chute structure 22 mounted upon the support l4 and securedthereto by bolts 24.

The forward side of each arc chute 22 is more clearly shown in Fig. 1,and is provided with a rectangular slot 25 at the lower end thereofthrough which a blade-like movable contact 28 may operate into and outof engagement with the stationary contact 16. The movable contact 28 ispreferably of inverted L-shaped blade construction having a bifurcatedarm 30', the two legs of which are pivoted at 32 a conducting bracket 34clamped about the tubular insulator l2. The pivotal connection- 32' isof the highpressure type, so that good electrical connection ismaintained at all times between the contact arm- 30 and the bracket 34.The right-hand side of the bracket 34 is provided ,with an externalcircuit terminal 36'. Thus when the interrupter is in the closed circuitposition, as shown, an electrical circuit is made therethrough from theterminal it, the stationary contact [6, moving contact 28, contact arms30, bracket 34' to the terminal 35.

Movement of the contact arm 36 about its pivot 32 to pen and closedcircuit positions is accomplished by an operating mechanism generallyindicated at 38. This operating mechanism' is'preferably a fluid: motorof the gas pressure opera-ted type, and includes a cylinder 40, a'piston "operative therein, and provided with a connecting rod 44'extending through the upper end of the cylinder 40. The connecting rod44 is coupled by a pair of links 46 to a crank arm 48 secured to across-shaft 50. The crossshaft 50, for example, may be journaled insuitable brackets 52 secured to the side of the pressure tank 6.

The cross-shaft 50 is provided at spaced intervals with three crank arms54 which, in turn, are coupled by an insulating operating rod 56 to themoving contact arms 30 of each respective pole unit. It will thus beseen that, if gas under pressure is admitted above the piston 42, thepiston will be moved downwardly within the cylinder 40 and theconnecting rod 44 will actuate crank arm 48 so as'to rock the crossshaft50 in a counterclockwise direction as viewed in Fig. 2. Since the crankarms 54 are secured to the cross-shaft 50, rotation of the latter willalso cause the crank arms 54 to be rotated in a counterclockwisedirection, thereby moving the operating rods 56 downwardly so as to swinthe contact arms 3|! about their pivotal points 32 towards theopen-circuit position.

It should be noted that each crank arm 54 is provided with a cam surface58 against which a roller 60 carried by the end of a bell crank 52 isadapted to ride. The bell crank 62 is pivoted upon a suitable support at64, and has its other free end .nivotally coupled to a valve stem I35carrying a valve 66 at its lower end which, in turn, is seated withinthe valve chamber Iii. The valve 68 normally seals the hollow airpassage within the insulator I2 from the pressure tank 6. It is thusseen that, as the three crank arms 54 start to rotate in acounterclockwise direction as viewed in Fig. 2, the cams 58, by engagingthe roller 60, will cause bell crank 62 to be rocked in a clockwisedirection, thereby depressing the valve stem 66 to open the valve 68. Asvalves 68 are opened, blast of compressed air from the storage tank 6rushes through each of the hollow insulators I2 through the throat-likepassage 20 between the contacts l6 and 2B. The cam 58 of each pole unitis preferably so positioned with respect to the roller 60 that the valve68 is o ened just prior to separation of the contacts l5 and 28, therebyinsuring a blast of arc-extinguishing gas at the surface of theseparating contacts when the arc is drawn. The are established betweenthe contacts I6 and I8 is blown into the arc chute 22 by the blast ofgas from the pressure tank 6 and extinguished in the arc chute. Theair-blast control cams 58 on the crank arms 54 are so shaped that, whenthe moving contacts 28 have reached their full open circuit position.the airblast valves 68 are again permitted to close so to shut off theblast of arc-extinguishing gas.

It will be obvious that, upon the admission of gas under pressure on thelower side of piston 42, the piston will be driven upwardly within thecylinder 40, and the moving contacts 26 will be moved to theclosed-circuit position in the reverse order above-described inconnection with the opening operation. In moving to the closed circuitposition the crank arms 54 are brought into engagement with stop members55 so positioned that the crank arms 54 and their associated operatingrods 56 form a slightly overcenter toggle arrangement, therebymaintaining the contacts 28 positively locked in the closed circuitposition.

In order that the opening and closing operation of the circuitinterrupter may be accomplished so as to meet the requirements of alloperating conditions, two control valves I0 and I2 are provided. Ingeneral, these control valves control the flow of air from the storagetank 6 to the operating cylinder 4!] to eflect the opening and closingoperations. The control valves "It and 12 are generally of the formbroadly illustrated in the aforesaid patent to A. H. Bakken, and aresecured to the operating cylinder 4%, as shown, to form a unit assembly.

As more fully disclosed in the aforesaid Bakken patent, this assemblyrests upon and is secured to flanges I4 and 16 by two short conduitsections 18 and 86. The conduit sections I8 and 80, in turn, communicaterespectively with relatively large conduits 82 and 84 extending throughthe side of the pressure tank 6 and terminating well within the interiorthereof. Each of the conduits 82 and 84 is provided with a partitiongenerally indicated at B6 in Fig. 2. and more specifically illustratedin Figs. 3 and 4. The partitions 86 are for the purpose of formingauxiliary gas storage compartments 83 and 85, respectively, forsupplying the compressed gas used in opening and closing theinterrupter. In order that the volume of the auxiliary tanks may bevaried to meet certain conditions, we prefer a construction for thepartitions 86 as more specifically shown in Figs. 3 and 4.

A threaded shaft 83 is secured at its left-hand end, as viewed in Fig.2, to the outer end of each of the conduits 82 and B4. Threaded to theshaft 88 is a metal collar 9i Surrounding the threaded rod 88 and heldin contact with the metallic collar 90 is a flanged washer 92 ofleather, rubber or other suitable material which is yieldingly urgedinto engagement with the inner ciroumference of the conduit 82 by aspring cupped washer 94. A nut 95 hearing against a washer 98 of smallerdiameter serves to lock the assem' bly in position with respect to thethreaded rod 88. The entire assembly is provided with a plu .rality ofthrough passages or orifices I00 which serve to admit air under pressurefrom the tank 6 to the auxiliary tank Within the conduits 82 and 34. Byenlarging the left-hand ends of the passages ID!) and providing the enlaged portions with threads, suitable plugs Ill? may be inserted for thepurpose of closing part of the passage to the flow of gas when desi ed.Thus if a men rapid or a slower replacement of is d sired from the tank5 to the am .rr tanks 83 and 85, some of the plugs Ill? are removed orreplaced as the circumstances demand.

The valves I?! and 72, which respectively control the flow of air fromthe au ary tanks; 3 and 85, are similar in construction. The alve I0,which is shown in cross-section (omprises a valve casing I04, the lowerface of which rests upon a flange 14 of conduit "8. The lower face ofthe casing I M is provided with a valve seat I05 which coacts with valveI08 of the poppet type. The valve M13 has a stem III! of usualconstruction provided at its end with a valve-lifting washer H2 coactingwith a p g I I4 for normally holding the alve closed, The inner chamberor the valve casing Hi4 communicates, by passage II6, to the upper endof the cylinder 48. The side of the valve casing I04 is also providedwith a bore or passage II! which communicates with the auxiliary chamber83 and the valve chamber I20 within an auxiliary valve casing I22.

The auxiliary valve casing I22 has an elec tromagneticaly operated valve624 which communicates, by passage I26, with a piston chamber I28 at theupper end of the valve casing I04.

The piston chamber Iithas. a piston: I3 3: operable therein which isnormally held in. the raised position by a spring I32. The lower end: orskirt of the piston I30 extends to a plurality of ports or bleedpassages I34 passing radially through theside of: the valve casing- I04.When the piston I 30 is in the raised position as shown in Fig. 5; theports I3' iare-opened thereby con.- neoting the space in the operatingcylinder 40 above the operating piston 42 with the atmosphere. It willbe observed that upon movement of the piston I30 downwardly; the portsI34 will be: closed so as to seal the passage I I6 and the cylinder404mm the atmosphere. The valve I 24 is actuated to the open position byan electromagnet I 38 which may be energizedby a suitable source ofelectrical potential (not shown), and is. moved tothe closed position bya spring I38;

When the interrupteris in the closed circuit position, the operatingmechanism. including the operating piston 42 is in the position as shownin Fig. 5. When in this position, an overload occurs, or if it isdesired for any other reason to open the-interrupter; electromagnetI'36-of the valve (0 is energized. The electromagnet I36 is preferablyconnected through and controlled by an auxiliary switch I40 mounteduponthe tank 6', as shown in Fig. l, auxiliary switch I401 is of usual andwell-known construction, further description thereofis deemedunnecessary for the purpose of understanding the present invention.

Upon energizing the electromagnet I36. valve I24 is opened to permit airunderpressure Within the auxiliary tank 93 to flow through the passage H8'; through the valve I24; the passage I26 into the piston chamber I281The piston I-30isthereupon driven downwardly against the force of springI32, thereby closing the vent ports I34. It will be notedthat the pistonI 30 is 50 disposed with respect to the upper end of the valve stem I I0that the ports I34 are substantially closed by the time the pistonengages the upper end of the stem Ht. Further downward movement ofthepiston I33 forces the valve stem H0 downwardly against the action ofthe valve spring I I4 toopenthe valve I08 and permit compressed air fromthe auxiliary tank 83 to liowthrough the passage H6 to the-space abovetheoperating piston42; The piston 42 will thereupon be moved downwardlyto actuate breaker contacts 28' to the open circuit position in themanner previously described.

When the piston 42- reaches the lower endof the cylinder 40, or. inother words, when the breaker has reached its full open circuitposition, the auxiliary switch I40 actuated by suitable linkage I42coupled. to the connecting rod 44 will interrupt the circuit energizingthe electromagnet I36 to allow valve I 2 4 to close. Thus, when thepressure is removed from the upper end of piston I30, springs I14 and I32 cause the piston I30 to move upwardly and'at the same time causevalve I08 to close. In order that the piston 42 may be moved downwardlyat a very high rate of speed so as to efiect opening of the contacts ofthe interrupter as quickl as possible, a relatively high gas pressure isessential at the beginning of the opening stroke. We have discoveredthat if the operating pressure is maintained substantially constant uponthe piston 42, it is dimcult to arrest the motion of the piston at theend of its stroke without injury to the operating mechanism or contactstructure.

Inasmuch as the In orderto" eliminate shock at. the: end of the openingstroke, but without: sacrificing speed of operation, we have decreasedthe force acting upon the piston 42 as the movement of: the pistonincreases. This. has. been accomplished by pro viding the auxiliary tank83 of: such volume as to produce the desiredv results. For example, ifthe airpressure within the maintank 6 is maintained at 1 50 poundspersquare inch, it is desirable to. provide the auxiliary. tank 83; ofvolume approximately one-half of' the volume of the operating cylinder4.0. As the. operating piston 42 is moved. to the open-circuit position,the air pressure within the auxiliary tank 83 decreases to approximately50- pounds per. square inch during the short interval of time requiredby the mechanism to reach the fullopen position. Thus, the averagepressure supplied bythe auxiliary tank 83 to the: piston 42 is much lessthan would be supplied by the main tank 6. In order to meet theserequirements, it is also necessary that a: very. small orifice orpassage lilll in the partition 8.6. be employed so as to avoidsubstantial replacement of air within the auxiliary tank 83 fromthemaintank 6 during the opening operation. By providinga number oforifices or passages I00 and providing means, such as plugs I02, as.shown in. Fig. 4, the proper rate of flow of air from the main tank 6into the auxiliary tank 83. may be obtained.

Theopening operation under conditions abovedescribed is similar to thatobtained by purely mechanical: means, utilizing acompression. springdirectly operative on the operating mechanism. Although, by using but a.limited quantity of air to-eflect the opening operation, the piston andoperating mechanism may be brought to rest without substantial shock orimpact, it is desirableto;provideshock-absorbing means of some form inorder to maintain the requisite highspeed operation. It is, of course,obvious that unless. the space ahead: of the operating piston 4.2-within the operating cylinder 40 is freely vented, the gas. containedtherein will be compressed during the opening stroke of the piston. Bycontrolling thedischarge of air ahead of the piston 42- during theopening stroke. the degree ofi' compression, particularly at the end ofthe stroke, maybe controlled" and: utilized" to provide ashock-absorbing. cushion for arresting the motion. of the piston. andthe associated moving parts. This control of the escape of air ahead ofthe piston; is provided: by the bleed passages or ports I231 through theside of the valve casing IM' of the control valven. It will be observedthat the control valve 12 isv similar in construction to the controlvalve L0, and that when control valve 10 is. opened: for admitting airto the operating cylinder 4:0; to effect an opening operationi. the;control valve 12-, which normally admits; air; at the lower end of thecylinder 43, to effect the; closing; operation, will be closed.

In practice, it is. desirable to arrange the ports L34. oi: the controlvalve 12, both with respect to size and number so that the air ahead ofthe pision, 42 during the opening operationmay reach compr ssionof.from. 55150, pounds p square inch at the end of; the opening stroke. It,of course, follows that this condition of compression within thecylinder 45 ahead of the, piston 42* persists only for a short time, andthat the air quickly bleeds from the cylinder 40 through the ports I34.Also, when the piston 42 reaches the full open-circuit position and thecontrol valve is closed as a result of deenergization of theelectromagnet I36, the air above the piston 42 quickly bleeds throughthe passage I I6 and ports I34 in the control valve I so as to permit areclosing operation of the interrupter by the admission of air to thelower side of the piston 42 through the valve 12.

In the event that it is desired to close the interrupter, theelectromagnet I36 of the control valve 12 is energized through theauxiliary switch I40 so as to admit air under pressure from theauxiliary tank 85 to the lower side of the operating piston 42. Inasmuchas the valves 12 and III are identical in construction, furtherdescription of the closing operation need not be given, except that itmay be stated that, during the closing operation, air above the piston42 is compressed so as to provide an elastic cushion for arresting themotion of the operating mechanism upon reaching the full closed-circuitposition, The degree of compression desired will, of course. be obtainedby the particular selection of size and number of exhaust ports I34provided in the control valve I0. Also upon reaching the closed circuitposition, or at a predetermined time before, the auxiliary switch I40will interrupt the control circuit to the electromagnet I36 of thecontrol valve I2 so as to deenergize the electromagnet and permit thevalve 12 to close in the manner above-described.

In the event that the circuit interrupter is closed while conditions ofoverload exist on the connected circuit, it becomes necessary to quicklyreverse the motion of the piston 42 so as to actuate the interrupter tothe open circuit position.

This operation becomes difiicult or, in fact, may

be impossible. unless provision is made to quickly relieve the pressureunder the piston 42. It will be observed that, during the closingstroke, compressed air has been dmitted below the piston 42, and that,upon reaching the closed-circuit position when conditions of overloadexist upon the breaker contacts, the piston would ordinarily have to bemoved against the residual air pressure remaining under the piston atthe end of the closing stroke.

In order that the piston 42 may be moved to the open-circuit positionunder the above conditions, a quick release valve is provided at thelower end of the cylinder 40, as more clearly shown in Fig. 5. Thisrelease valve, for instance, may comprise a valve member I44 carried bya stem I40 slidably operative through the lower end 01! the cylinder 40and biased to the closed position by a spring I48 or other suitablemeans. The valve I44 may be moved to the open position by an operatingrod I50 secured at its lower end to the valve I44 and at its upper endto the lower end of the connecting rod 44. More specifically, the upperend of rod I50 is provided with a circular head I52 slidable within thebore of the connecting rod 44 and adapted to be engaged at its lowershoulders by a packing and guide sleeve I54 threaded into the lower endof the connecting rod 44. The operating rod I 50 is preferably of alength such that when the piston 42 reaches the upper limit of itstravel, valve I44 will be fully opened, thereby quickly exhausting theair below the piston 42 to atmosphere. Thus the piston 42 is free tomove downwardly as under normal conditions of operation. It will benoted that only a short travel in the downward direction is required ofthe piston 42 before valve I44 is closed, thereby permitting the airunder the piston 42 to be compressed for the purpose of cushioning thepiston at the end of its opening stroke.

Inasmuch as the control valves 10 and I2 are electrically operated bytheir respective electromagnets I36, a condition may prevail whereinthetwo electromagnets may become energized simultaneously. Thus, if equalforces were admitted on either side of the operating piston 42, theoperating mechanism would become inoperative and no movement in eitherthe opening or closing direction would take place. Since it is a primerequisite to provide overload protection for the connected circuit, itis desirable to insure opening operation even under such abnormalconditions of simultaneous energization of both control valves. Thedesired reliability of operation has been accomplished by making theauxiliary tank 83 larger than the auxiliary tank 85, so that in theevent that valves I0 and I2 are simultaneously opened, even though eachtank 83 and B5 is initially at the same pressure, the volume of tank 83being larger will give a higher average pressure and exert apredominating force upon the piston 42 and cause it to be moved towardthe open-circuit position. The auxiliary tanks 83 and 85 are soproportioned that sufllcient movement of the interrupter toward the opencircuit position will be obtained to effectively interrupt the circuit.The volume of the auxiliary tanks 83 and 85 may readily be changed tosuit operating conditions by adjusting the partition members 86 axiallyalong the threaded rods in a manner previously described.

We have discovered that by utilizing an operating mechanism of the typeabove-described in a circuit interrupter capable of interrupting1,500,000 kv.-a. at 15,000 volts, contact opening speeds in excess of2'7 feet per second were obtainable. In spite of this high-speed contactmovement, the operating mechanism was brought to rest at the end of itsstroke without subjecting the mechanism or its associated parts tosevere shocks 0r strains.

Furthermore, the above-described mechanism is in effect trip-free inthat opening of the interrupter contacts immediately following a closureunder conditions of overload on the connected circuit is obtained withthe same degree of effectiveness as during a, straight openingoperation. This trip-free effect, however, is obtained without the useof latches or mechanically-operated trip-free mechanisms.

Although we have shown and described a. specific circuit interrupter anda particular operating mechanism therefor, it is to be understood thatthe same is for the purpose of illustration and that changes andmodifications may be made by those skilled in the art without departingfrom the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, separable contacts operating means foractuating said contacts to open and closed positions, said operatingmeans including a fluid pressure actuated device, a main source of fluidunder pressure, an auxiliary sourc: of fluid normally maintained underpressure derived from said main source, and valve means between saidauxiliary source and said pressure actuated device for admitting iluidunder pressure from said auxiliary source to said pressure actuateddevice, said auxiliary source having a capacity to operate said pressureactuated device completely and but once without replacement of fluidfrom said main source of fluid pressure.

2. In a circuit interrupter, separable contacts.

operating means for actuating said contacts to open and closedpositions, said operating means including a fluid pressure actuateddevice, a main source of fluid under pressure, an auxiliary source offluid under pressure derived from said main source, and valve means foradmitting fluid under pressure from said auxiliary source to saidpressure actuated device, said auxiliary source having a capacity tooperate said pressure actuated device but once without replacement offluid from said main source of fluid pressure, said auxiliary source offluid pressure having a permanent connection with said main source, andmeans controlling the flow of fluid from said main source of pressur tosaid auxiliary source to prevent substantial replacement of fluid insaid auxiliary source during a contact operation.

3. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a cylinder, a piston in said cylinder operativelycoupled to at least one of said contacts, a main tank for storing fluidunder pressure, an auxiliary tank deriving fluid and normally maintainedunder pressure from said main tank and supplying all of the fluid foroperating said piston in one direction, and valve means for admittingfluid from said auxiliary tank to said cylinder to actuate said piston,the volume of said auxiliary tank being so proportioned with respect tothe volume of said cylinder that the force exerted upon said pistondecreases substantially with the distance traveled by said piston.

4. In a circuit interrupter, separabl contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a cylinder, a piston in said cylinder operativelycoupled to at least one of said contacts, a main tank for storing fluidunder pressure, an auxiliary tank deriving fluid under pressure fromsaid main tank, and valve means between said auxiliary tank and cylinderfor admitting fluid from said auxiliary tank to said cylinder to actuatesaid piston, and means disposed between said main tank and saidauxiliary tank for controlling the rate of flow of fluid therebetween,said means admitting substantially no fluid into said auxiliary tankdurin the operation of said operating means.

5. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, a source of gas under pressure, valve meansfor admitting gas from said source to at least one side of said pistonfor actuating said operating means, and means controlling the escape ofgas from ahead of said piston during movement thereof in a givendirection to provide a shock absorbing cushlon of gas for arrestin themotion of said piston at the end of its stroke.

6. In a circuit interrupter, contact means, operating means including acylinder and a pist'on operative therein for moving said contact meansto open and closed positions, a, source of gas under pressure, openingand closing valves for alternately admitting gas under pressure fromsaid source to opposite sides of said piston to respectively cause saidpiston to move to open and closed circuit positions, and means operatedin accordance with the position of said valves for controlling theescape of gas ahead of said piston during movement thereof in either theaircuit opening or closing direction, said last-named means enabling gasto be compressed ahead of said piston to assist in bringing said pistonto rest at the end of its stroke.

7. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, a source of gas under pressure, opening andclosing valves for alternately admitting gas under pressure from saidsource to opposite sides of said piston to respectively cause saidpiston to move to open and closed circuit positions, and meanscontrolling the escape of gas ahead of said piston during movementthereof in either the circuit opening or closing direction to provide ashock absorbing cushion of gas for arresting the motion of said pistonat the end of its stroke, and additional means for quickly exhaustingthe gas on the high pressure side of said piston at the end of itsstroke to enable the piston to be reversed immediately withoutinterference from excessive back pressure.

8. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, a source of gas under pressure, opening andclosing valves for alternately admitting gas under pressure from saidsource to opposite sides of said piston to respectively cause saidpiston to move to open and closed circuit positions, means operated inaccordance with the position of said valves for controlling the escapeof gas ahead of said piston during movement thereof in either thecircuit opening or closing direction to cause gas to be compressed ahead'of said piston to assist in bringing said piston to rest at the end ofits stroke, and means for quickly relieving the gas pressure on the highpressure side of said piston at the "end of its stroke to enable saidpiston to be reversed immediately free fromv back pressure.

9. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, means for selectively admitting gas underpressure to either side of said piston for causing said piston to moveto open and closed circuit positions, valve means controlling the escapeof gas ahead of said piston to provide an elastic cushion for bringingsaid piston to rest at the end of its stroke, and additional valve meansoperative at the end of the stroke of said piston for releasing thepressure on the high pressure side of said piston so as to enable saidpiston to be reversed without time delay.

10. In a circuit interrupter, con-tact means, operating means includinga cylinder and a piston operative therein for moving said contact meansto open and closed positions, said piston having a tubular connectingrod secured thereto, means for selectively admitting gas under pressureto either side of said piston for causing said piston to move to openand closed circuit positions, a gas escape valve for said cylinder, saidvalve having a stem extending through said cylinder and being slidablyoperative within said tubular connecting rod, and means for connectingsaid stem to said connecting rod for opening said valve upon movement ofsaid conta'cts to the closed circuit position, said valve releasing thegas pressure ahead of said piston to enable said contacts to be movedwithout time delay to the open circuit position.

ll. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, means for selectively admitting gas underpressure to either side of said piston for causing said piston to moveto open and closed circuit positions, a gas escape valve for saidcylinder, and means disposed within said cylinder for operativelycoupling said piston to said gas escape valve for opening said valveupon movement of said contacts to the closed circuit position, saidvalve releasing the gas pressure ahead of said piston to enable saidcontacts to be moved without time delay to the open circuit position.

12. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed .positions, said operatingmeans including a fluid pressure actuated device, a main source of fluidunder pressure, a first auxiliary source of fluid under pressure derivedfrom said main source, a second auxiliary source of fluid under pressurealso derived from said main source, valve means for admitting fluidunder pressure from said first auxiliary source to said pressureactuated device for causing said device to be moved in one direction,and a second valve means for admitting fluid under pressure from saidsecond auxiliary source to said pressure actuated device for causingsaid device to be moved in the reverse direction, one of said auxiliarysources of pressure having a larger capacity than the other auxiliarysource to cause said pressure actuated device to be actuated always inthe same direction when fluid is admitted thereto simultaneously fromboth auxiliary sources of pressure.

13. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a piston, means for supplying fluid under pressure toone side of said piston to move said contacts to one of said positions,and means for supplying fluid under pressure to the other side of saidpiston to move said contacts to the other position, the average pressuresupplied by one of said pressure supply means being greater than theaverage pressure supplied by the other pressure supply means for causingsaid piston to be moved always in the same direction when fluid pressureis supplied simultaneously from both supply means to opposite sides ofsaid piston,

14. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a piston, a main source of fluid under pressure, anauxiliary source of fluid under pressure derived from said main source,means for admitting fluid from said auxiliary source to one side of saidpiston to move said contacts to the open position, a second auxiliarysource of fluid under pressure also derived from said main source, andmeans for admitting fluid from said second auxiliary source to the otherside of said piston for moving said contacts to the closed position,said first auxiliary source having a fluid capacity capable ofdelivering fluid at a higher average pressure than said second auxiliarysource to cause said piston to move said contacts to the open positionwhen fluid is supplied to both sides of said piston from said respectivesources.

15. In a circuit interrupter, contact means for opening and closing thecircuit, a fluid motor for actuating said contact means, a source offluid under pressure, a chamber containing a quantity said fluid underpressure suflicient to operate said fluid motor to actuate said contactmeans in one direction with a large reduction in pressure in saidchamber, valve means for controlling the flow of fluid from said chamberto said fluid motor, and a connection from said chamber to said sourceof fluid under pressure automatically operable immediately upon saidreduction in pressure in the chamber to begin restoring the pressure inthe chamber to full value.

16. In a circuit interrupter, contact means for opening and closing thecircuit, a fluid motor for actuating said contact means, a source offluid under pressure, a chamber containing a quantity of said fluidunder pressure, valve means for controlling the flow of fluid from saidchamber to said fluid motor, a restricted passage from said source offluid under pressure to said chamber, the size of said chamber and thesize of said restricted passage being such that there is a largereduction in pressure in said chamber upon the actuation of said contactmeans by said fluid motor, and said restricted passage being open duringactuation of said contact means to permit the restoration of fullpressure in said chamber from said source.

17. In a circuit interrupter, contact means for opening and closing thecircuit, a fluid motor for actuating said contact means, a source offluid under pressure, and a control device between said fluid motor andsaid source of fluid under pressure operable to apply pressure to saidfluid motor at substantially the full pressure of said source at thebeginning of the operation of said contact means and to decrease thepressure during the operation of said contact means until only a muchlower pressure is applied at the very end of the operation.

18. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means, asource of fluid under pressure, valve means for admitting fluid fromsaid source to actuate said piston in one direction, and means forrelieving said pressure to permit return movement of said piston byproviding a large vent apart from said valve means for quickly relievingthe pressure during the first part of the return movement and meansapart from said large vent providing a restricted vent for relieving thepressure slowly and cushioning the later part of the return movement.

19. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a cylinder, a piston in said cylinder operativelycoupled to at least one of said contacts, a main tank for storing fluidunder pressure, an auxiliary tank deriving fluid under pressure fromsaid main tank and normally maintained under sufficient pressure toactuate the piston, and valve means for admitting fluid from saidauxiliary tank to said cylinder to actuate said piston, means disposedbetween said main tank and said auxiliary tank for controlling the flowof fluid therebetween, and the pressure exerted on said piston from saidauxiliary tank being substantially unaffected by the pressure in themain tank during the period that the piston is being moved.

20. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a cylinder, a piston in said cylinder operativelycoupled to at least one of said contacts, a main tank for storing fluidunder pressure, an auxiliary tank deriving fluid under pressure fromsaid main tank, means for caus ing a blast of fluid from said main tankto flow across said contacts as they separate to extinguish the arc, andvalve means for admitting fluid from said auxiliary tank to saidcylinder to actuate said piston, means disposed between said main tankand said auxiliary tank for controlling the flow of fluid therebetween,and the pressure exerted on said piston from said auxiliary tank beingsubstantially unaffected by the pressure in the main tank during theperiod that the piston is being moved.

21. In an electric circuit breaker, a pair of relatively movablecontacts separable to draw an arc therebetween, a fluid motor forproducing relative movement between said contacts, a main source offluid under pressure, means for introducing a blast of fluid driven bythe pressure of said main source adjacent said contacts forarcextinguishing purposes, an auxiliary source of fluid under pressuresupplied from said main source for operating said fluid motor to producerelative movement between said contacts, and said auxiliary sourcesupplying substantially all of the fluid to operate said motor at anaverage pressure less than the pressure that would be supplied from saidmain source.

22. In an electric circuit breaker, a pair of relatively movablecontacts separable to draw an arc therebetween, a source of fluid underpressure, means for introducing a blast of fluid from said sourceadjacent said contacts for arc-extinguishing purposes, a fluid motor, asecond source of fluid under pressure connected to supply only saidfluid motor, means for operating said motor from said second source toproduce relative movement between said contacts, and the pressuresupplied to the fluid motor from the second source being substantiallyunaffected by the pressure of said first-mentioned source duringoperation of the fluid motor.

23. In a circuit interrupter, contact, means, operating means includinga cylinder and a piston operative therein for moving said contact meansto open and closed positions, a source of gas under pressure, valvemeans for admitting gas from said source to at least one side of saidpiston for actuating said operating means, means controlling the escapeof gas from ahead of said piston during movement thereof in a givendirection to provide a shock absorbing cushion of gas for arresting themotion of said piston at the end of its stroke, and valve controlledoutlet means near one end of the cylinder operated to open widely andpermit quick exhaust of gas only when the piston is near the other endof the cylinder to permit quick movement of the piston during at leastthe early part of its movement toward the end having said valvecontrolled outlet means.

24. In a circuit interrupter, contact means, operating means including acylinder and a piston operative therein for moving said contact means toopen and closed positions, a source of gas under pressure, valve meansfor admitting gas from said source to at least one side of said pistonfor actuating said operating means to close the contacts, meanscontrolling the escape of gas from ahead of said piston during movementthereof in closing direction to provide a shock absorbing cushion of gasfor arresting the motion of said piston at the end of its closingstroke, and valve controlled outlet means near the end of the cylindertoward which the piston moves during opening movement operated to openwidely and permit quick exhaust of gas only when the piston is near theend of the cylinder Where the contacts are closed.

25. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a fluid pressure actuated device, a main source of fluidunder pressure, an auxiliary source of fluid under pressure derived fromsaid main source, and valve means for admitting fluid under pressurefrom said auxiliary source to said pressure actuated device, saidauxiliary source having a capacity to operate said pressure actuateddevice completely and but once without replacement of fluid from saidmain source of fluid pressure, and another valve means for admittingfluid from said main source to blast through the are formed at saidseparable contacts to extinguish it independently of the pressure ofsaid auxiliary source.

26. In a circuit interrupter, separable contacts, operating means foractuating said contacts to open and closed positions, said operatingmeans including a cylinder, a piston in said cylinder operativelycoupled to at least one of said contacts, a main tank for storing fluidunder pressure, an auxiliary tank deriving fluid under pressure fromsaid main tank and supplying all of the fluid for operating said pistonin one direction, and valve means for admitting fluid from saidauxiliary tank to said cylinder to actuate said piston, the volume ofsaid auxiliary tank being so proportioned with respect to the volume ofsaid cylinder that the force exerted upon said piston decreasessubstantially with the distance traveled by said piston, and a blastvalve for admitting fluid from said main tank to extinguish the areformed at said separable contacts substantially independently of thepressure in said auxiliary tank.

LEON R. LUDWIG. BENJAMIN P. BAKER.

